Beam forming network for feeding short wall slotted waveguide arrays

ABSTRACT

An example method for a beamforming network for feeding short wall slotted waveguide arrays. The beamforming network may include six beamforming network outputs, where each beamforming network output is coupled to one of a set of waveguide inputs. Further, the beamforming network may include a cascaded set of dividers configured to split electromagnetic energy from a beamforming network input to the six phase-adjustment sections. The cascade may include a first level of the cascade configured to split the electromagnetic energy from the beamforming network input into two first-level beamforming waveguides, a second level configured to split the electromagnetic energy from each of two first-level beamforming waveguides into two respective second-level beamforming waveguides, and a third level of the cascade configured to split the electromagnetic energy from one of two respective second-level beamforming waveguides into two respective third-level beamforming waveguides.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Radio detection and ranging (RADAR) systems can be used to activelyestimate distances to environmental features by emitting radio signalsand detecting returning reflected signals. Distances to radio-reflectivefeatures can be determined according to the time delay betweentransmission and reception. The radar system can emit a signal thatvaries in frequency over time, such as a signal with a time-varyingfrequency ramp, and then relate the difference in frequency between theemitted signal and the reflected signal to a range estimate. Somesystems may also estimate relative motion of reflective objects based onDoppler frequency shifts in the received reflected signals.

Directional antennas can be used for the transmission and/or receptionof signals to associate each range estimate with a bearing. Moregenerally, directional antennas can also be used to focus radiatedenergy on a given field of view of interest. Combining the measureddistances and the directional information allows for the surroundingenvironment features to be mapped. The radar sensor can thus be used,for instance, by an autonomous vehicle control system to avoid obstaclesindicated by the sensor information.

Some example automotive radar systems may be configured to operate at anelectromagnetic wave frequency of 77 Giga-Hertz (GHz), which correspondsto a millimeter (mm) wave electromagnetic wave length (e.g., 3.9 mm for77 GHz). These radar systems may use antennas that can to focus theradiated energy into tight beams in order to enable the radar system tomeasure an environment with high accuracy, such as an environment aroundan autonomous vehicle. Such antennas may be compact (typically withrectangular form factors), efficient (i.e., with little of the 77 GHzenergy lost to heat in the antenna or reflected back into thetransmitter electronics), and low cost and easy to manufacture (i.e.,radar systems with these antennas can be made in high volume).

SUMMARY

In a first aspect, the present application discloses embodiments thatrelate to a radar system. The radar system may include six radiatingwaveguides located in a waveguide layer. Each radiating waveguide mayhave a radiating waveguide input. Additionally, each radiating waveguidemay have a height and a width equal that are equal to that of each otherradiating waveguides. The radiating waveguides may be aligned on a planedefined by a center of the width of the radiating waveguide and a lengthof the radiating waveguide. Further, each radiating waveguide is coupledto at least one radiating element located in a radiating layer. Theradar system may also include a beamforming network located in thewaveguide layer. The beamforming network may include a beamformingnetwork input. Additionally, the beamforming network may include sixbeamforming network outputs, where each beamforming network output iscoupled to one of the radiating waveguide inputs. Further, thebeamforming network may include six phase-adjustment sections. Each ofthe phase-adjustment sections may be coupled a respective one of the sixcascade outputs. Still further, the beamforming network may include acascaded set of dividers configured to split electromagnetic energy fromthe beamforming network input to the six phase-adjustment sections. Thecascade may include a first level of the cascade configured to split theelectromagnetic energy from the beamforming network input into twofirst-level beamforming waveguides. The cascade may also include asecond level of the cascade configured to split the electromagneticenergy from each of two first-level beamforming waveguides into tworespective second-level beamforming waveguides for each respectivefirst-level beamforming waveguide. One of two respective second-levelbeamforming waveguides for each respective first-level beamformingwaveguide may be coupled to one of the phase-adjustment sections. Thecascade may also include a third level of the cascade configured tosplit the electromagnetic energy from one of two respective second-levelbeamforming waveguides for each respective first-level beamformingwaveguide into two respective third-level beamforming waveguides foreach respective second-level beamforming waveguides. Each of thethird-level beamforming waveguides may be coupled to a respective one ofthe phase-adjustment sections.

In another aspect, the present application describes a method ofradiating electromagnetic energy. The method includes receivingelectromagnetic energy by a beamforming network input. The method alsoincludes splitting the received electromagnetic energy with a cascadedset of dividers to form six divided electromagnetic energy streamscoupled into six phase-adjustment sections. The splitting includessplitting the electromagnetic energy from the beamforming network inputinto two first-level beamforming waveguides by a first level of thecascade. The splitting also includes splitting the electromagneticenergy from each of two first-level beamforming waveguides into tworespective second-level beamforming waveguides for each respectivefirst-level beamforming waveguide by a second level of the cascade,where one of two respective second-level beamforming waveguides for eachrespective first-level beamforming waveguide is coupled to one of thephase-adjustment sections. The splitting also includes splitting theelectromagnetic energy from one of two respective second-levelbeamforming waveguides for each respective first-level beamformingwaveguide into two respective third-level beamforming waveguides foreach respective second-level beamforming waveguides by a third level ofthe cascade, where each of the third-level beamforming waveguides iscoupled to a respective one of the phase-adjustment sections. The methodfurther includes adjusting the phase of each of the six electromagneticenergy streams by the six phase-adjustment sections to form six phaseadjusted electromagnetic energy streams. The method additionallyincludes coupling each of the six phase adjusted electromagnetic energystreams into a respective radiating waveguide of six radiatingwaveguides located in a waveguide layer, where each radiating waveguideis coupled to at least one radiating element located in a radiatinglayer. The method yet further includes for each radiating waveguide,radiating at least a portion of the phase adjusted electromagneticenergy stream by a radiating element.

In yet another aspect, the present application describes beamformingnetwork located in a waveguide layer. The beamforming network includes abeamforming network input. Additionally, the beamforming networkincludes six beamforming network outputs, where each beamforming networkoutput is coupled to a respective waveguide input of a set ofwaveguides. The beamforming network further includes a cascaded set ofdividers coupled to six phase-adjustment sections, where each cascade isconfigured to distribute electromagnetic energy from the beamformingnetwork input to the six phase-adjustment sections based on apredetermined taper profile. The cascade may include a first level ofthe cascade configured to approximately evenly split the electromagneticenergy from the beamforming network input into two first-levelbeamforming waveguides. The cascade may further include a second levelof the cascade configured to split the electromagnetic energy from eachof two first-level beamforming waveguides into two respectivesecond-level beamforming waveguides for each respective first-levelbeamforming waveguide, where one of two respective second-levelbeamforming waveguides for each respective first-level beamformingwaveguide is coupled to one of the phase-adjustment sections. And, thecascade may also include a third level of the cascade configured tosplit the electromagnetic energy from one of two respective second-levelbeamforming waveguides for each respective first-level beamformingwaveguide into two respective third-level beamforming waveguides foreach respective second-level beamforming waveguides, where each of thethird-level beamforming waveguides is coupled to a respective one of thephase-adjustment sections. Additionally, each phase-adjustment sectionhas a respective length that provides a respective phase offset for eachwaveguide.

In another aspect, the present application describes an apparatus forradiating electromagnetic energy. The apparatus includes means forreceiving electromagnetic energy. The apparatus also includes means forsplitting the received electromagnetic energy to form six dividedelectromagnetic energy streams. The means for splitting includessplitting the electromagnetic energy from the means for receiving intotwo first-level beamforming waveguides. The means for splitting alsoincludes splitting the electromagnetic energy from each of twofirst-level beamforming waveguides into two respective second-levelbeamforming waveguides for each respective first-level beamformingwaveguide, where one of two respective second-level beamformingwaveguides for each respective first-level beamforming waveguide iscoupled to one of the means for phase-adjustment. The means forsplitting also includes splitting the electromagnetic energy from one oftwo respective second-level beamforming waveguides for each respectivefirst-level beamforming waveguide into two respective third-levelbeamforming waveguides for each respective second-level beamformingwaveguides, where each of the third-level beamforming waveguides iscoupled to one of the means for phase-adjustment. The method furtherincludes means for phase-adjustment of each of the six radiationelectromagnetic energy streams to form six phase adjustedelectromagnetic energy streams. The method additionally includes meansfor coupling each of the six phase adjusted electromagnetic energystreams into a respective radiating waveguide of six radiatingwaveguides located in a waveguide layer, where each radiating waveguideis coupled to at least means for radiating located in a radiating layer.The method yet further includes for each radiating waveguide, means forradiating at least a portion of the phase adjusted electromagneticenergy stream.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an example of radiating slots on a waveguide.

FIG. 2 illustrates an example waveguide with ten radiating Z-Slots.

FIG. 3 illustrates an example radar system with six radiatingwaveguides.

FIG. 4 illustrates an example radar system with six radiating waveguidesand a waveguide feed system.

FIG. 5 illustrates a network of wave-dividing channels of an examplesystem, in accordance with an example embodiment.

FIG. 6 illustrates an alternate view of the network of wave-dividingchannels of FIG. 5, in accordance with an example embodiment.

FIG. 7 is an example method for radiating electromagnetic energy with anexample waveguide antenna.

FIG. 8 illustrates an exploded view of a portion of an example waveguideapparatus.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying figures, which form a part hereof. In the figures, similarsymbols typically identify similar components, unless context dictatesotherwise. The illustrative embodiments described in the detaileddescription, figures, and claims are not meant to be limiting. Otherembodiments may be utilized, and other changes may be made, withoutdeparting from the scope of the subject matter presented herein. It willbe readily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

The following detailed description relates to an apparatus and methodfor a beamforming network for feeding short wall slotted waveguidearrays, such as an automotive, high-frequency (e.g., 77 GHz) radarantenna used for millimeter electromagnetic wave signaling. In practice,waveguides and waveguide antennas may be fabricated in various ways. Forinstance, for printed waveguide transmission line (PWTL) antennas, aconductive adhesive thin film can be used to adhere the various layersof the PWTL antennas together. However, the performance of such anantenna may be less than optimal because the radiation efficiency andgain of the antenna is highly dependent on the conductivity of theconductive adhesive layer and its alignment and the time of thelaminations. Additionally, the performance of such a waveguide may beless than optimal because the PWTL construction may introducetransmission losses into the waveguide.

For this reason, soldering (or metal to metal fusion) may provide betteradhesion between metal layers, such as an aluminum sheet metal layer(with copper plating) adhered to copper foil/sheets. Sheet metals may beadhered to other sheet metals rather than foils, in other examples.Additionally, in some examples, before metal layers are adhered, variousstructures may be created in the respective metal layers. Afteradhesion, the various structures may form a waveguide unit, such as awaveguide unit for use in autonomous vehicles.

In one example a bottom layer may have a port feature. The port featuremay enable electromagnetic energy (such as an electromagnetic wave) toenter the waveguide unit. The port feature may allow electromagneticenergy from a signal generation unit to be coupled into the waveguideunit for transmission into the environment around the waveguide unit (oraround a vehicle to which the waveguide unit is coupled). Additionally,the port may enable electromagnetic energy within the waveguide unit tobe coupled out of the waveguide unit. For example, when the waveguideunit receives electromagnetic energy, it may couple the electromagneticenergy out the port to processing electronics. Therefore, the port mayfunction as a gateway between the waveguide unit and the signalgeneration and/or processing electronics that may operate the waveguideunit.

A middle layer may be coupled to both the bottom layer and the toplayer. The middle layer may be referred to as a waveguide layer. Themiddle layer may have at least one waveguide in it. The waveguide mayhave a width that is measured with respect to a thickness of the middlelayer (e.g. a maximum width of the waveguide in the middle layer may beequal to the thickness of the middle layer). Further, the height of thewaveguide may be measured in the direction parallel to the plane inwhich the layers are adhered to each other. Additionally, in someexamples, the width of the waveguide is larger than the height of thewaveguide. The waveguides in the waveguide layer may perform severalfunctions, such as routing, joining, and splitting of theelectromagnetic energy.

In one example, the middle layer may receive electromagnetic energy froma port in the bottom layer. The waveguide of the middle layer may splitthe electromagnetic energy and route the electromagnetic energy to atleast one radiating structure located in the top layer. In anotherexample, the middle layer may receive electromagnetic energy from the atleast one radiating structure in the top layer. The waveguides of themiddle layer may join the electromagnetic energy and route theelectromagnetic energy to the port located in the bottom layer.

The top layer may include at least one radiating structure. Theradiating structure may be etched, cut, or otherwise located on sheet ofmetal that is adhered to the middle layer. The radiating structure maybe configured to perform at least one of two functions. First, theradiating structure may be configured to radiate electromagnetic energypropagating inside the waveguide out into free space (i.e. the radiatingstructure converts the guided energy in the waveguide into radiatedenergy propagating in free space). Second, the radiating structure maybe configured to receive electromagnetic energy propagating in freespace and route the received energy into the waveguide (i.e. theradiating structure converts the energy from free space into guidedenergy propagating in a waveguide).

In some embodiments, the radiating structure may take the form of aradiating slot. The radiating slot may have a length dimension. Thelength dimension may correspond to a resonant frequency of operation forthe slot. The resonant frequency of the slot may be equal to, orsubstantially close to, the frequency of the electromagnetic energy inthe waveguide. For example, the length of the slot may be resonant atapproximate half the wavelength of the electromagnetic energy in thewaveguide. In some examples, the resonant length of the slot may begreater than the height of the waveguide. If the slot was longer thanthe waveguide, energy may not couple to the slot correctly, as theeffective length of the slot is the length of the slot to which energyinside the waveguide can couple (i.e. the portion of the slot that isopen to the waveguide). Thus, the electromagnetic energy may not radiatefrom the slot. However, in some examples, the slot may be shaped in away that the total length of the slot is equal to the resonant length,but the slot still fits within a height of the waveguide. These shapesmay be Z, S, 7, or other similar shapes (e.g. the total length of theshape is the total slot effective length, the bend of the shape allows alonger slot in a smaller space). Therefore, the slot may function like aslot that is longer than the height of the waveguide but still resonateat the desired radiation frequency.

In one example of fabrication of the waveguide unit, the structureslocated on each layer may be placed, cut, etched, or milled on eachlayer before the layers are adhered together. Thus, the location of theelements may be located fairly precisely on each layer when each ismachined. When the bottom layer is adhered to the middle layer, the portmay be located directly under a waveguide section. Thus, the entire portmay be open to the waveguide in the middle layer. Additionally, theradiating elements of the top layer may be positioned in a way that theentire radiating element may be located directly above a waveguidesection. Thus, the entire radiating element may be open to the waveguidein the middle layer.

FIGS. 1-4 illustrate example waveguides and radar systems in whichexample apparatuses for folded radiation slots for short wall waveguideradiation may be implemented.

Referring now to the figures, FIG. 1 illustrates an example of radiatingslots (104, 106 a, 106 b) on a waveguide 102 in waveguide unit 100. Itshould be understood that waveguide unit 100 presents one possibleconfiguration of radiating slots (104, 106 a, 106 b) on a waveguide 102.

It should also be understood that a given application of such an antennamay determine appropriate dimensions and sizes for both the radiatingslots (104, 106 a, 106 b) and the waveguide 102. For instance, asdiscussed above, some example radar systems may be configured to operateat an electromagnetic wave frequency of 77 GHz, which corresponds to a3.9 millimeter electromagnetic wave length. At this frequency, thechannels, ports, etc. of an apparatus fabricated by way of method 100may be of given dimensions appropriated for the 77 GHz frequency. Otherexample antennas and antenna applications are possible as well.

Waveguide 102 of waveguide unit 100 has a height of H and a width of W.As shown in FIG. 1, the height of the waveguide extends in the Ydirection and the width extends in the Z direction. Both the height andwidth of the waveguide may be chosen based on a frequency of operationfor the waveguide 102. For example, when operating waveguide 102 at 77GHz, the waveguide 102 may be constructed with a height H and width W toallow propagation of 77 GHz wave. An electromagnetic wave may propagatethrough the waveguide in the X direction. In some examples, thewaveguide may have a standard size such as a WR-12 or WR-10. A WR-12waveguide may support the propagation of electromagnetic waves between60 GHz (5 mm wavelength) and 90 GHz (3.33 mm wavelength). Additionally,a WR-12 waveguide may have the internal dimensions of approximately 3.1mm by 1.55 mm. A WR-10 waveguide may support the propagation ofelectromagnetic waves between 75 GHz (4 mm wavelength) and 110 GHz(2.727 mm wavelength). Additionally, a WR-12 waveguide may have theinternal dimensions of approximately 2.54 mm by 1.27 mm. The dimensionsof the WR-12 and the WR-10 waveguides are presented for examples. Otherdimension are possible as well.

Waveguide 102 may be further configured to radiate the electromagneticenergy that is propagating through the waveguide. The radiating slots(104, 106 a, 106 b), as shown in FIG. 1, may be located on the surfaceof the waveguide 102. Additionally, as shown in FIG. 1, the radiatingslots (104, 106 a, 106 b) may be located primarily on the side of thewaveguide 102 with the height H dimension. Further, the radiating slots(104, 106 a, 106 b) may be configured to radiate electromagnetic energyin the Z direction.

The linear slot 104 may be a traditional waveguide radiating slot. Alinear slot 104 may have a polarization in the same direction as thelong dimension of the slot. The long dimension of the linear slot 104,measured in the Y direction, may be approximately one-half of thewavelength of the electromagnetic energy that is propagating through thewaveguide. At 77 Ghz, the long dimension of the linear slot 104 may beapproximately 1.95 mm to make the linear slot resonant. As shown in FIG.1, the linear slot 104 may have a long dimension that is larger than theheight H of the waveguide 102. Thus, the linear slot 104 may be too longto fit on just the side of the waveguide having the height H dimension.The linear slot 104 may continue on to the top and bottom of thewaveguide 102. Additionally, a rotation of the linear slot 104 may beadjusted with respect to the orientation of the waveguide. By rotatingthe linear slot 104, an impedance of the linear slot 104 and apolarization and intensity of the radiation may be adjusted.

Additionally, the linear slot 104 has a width dimension that may bemeasured in the X direction. Generally, the width of the waveguide maybe varied to adjust the bandwidth of the linear slot 104. In manyembodiments, the width of the linear slot 104 may be approximately 10%of the wavelength of the electromagnetic energy that is propagatingthrough the waveguide. At 77 Ghz, the width of the linear slot 104 maybe approximately 0.39 mm. However, the width of the linear slot 104 maybe made wider or narrower in various embodiments.

However, in some situations, it may not be practical or possible for awaveguide 102 to have a slot on any side other than the side of thewaveguide having the height H dimension. For example, some manufacturingprocesses may create a waveguide structure in layers. The layers maycause only one side of the waveguide to be exposed to free space. Whenthe layers are created, the top and bottom of the respective waveguidemay not be exposed to free space. Thus, a radiating slot that extends tothe top and bottom of the waveguide would not be fully exposed to freespace, and therefore would not function correctly, in someconfigurations of the waveguide. Therefore, in some embodiments, foldedslots 106 a and 106 b may be used to radiate electromagnetic energy fromthe inside the waveguide.

A waveguide may include slots of varied dimensions, such as folded slots106 a and 106 b, in order to radiate electromagnetic energy. Forexample, folded slots 106 a and 106 b may be used on a waveguide insituations when a half-wavelength sized slot cannot fit on the side ofthe waveguide. The folded slots 106 a and 106 b each may have anassociated length and width. The total length of the folded slots 106 aand 106 b, as measured through a curve or a bend in the folded slot, maybe approximately equal to half the wavelength of the electromagneticenergy in the wave. Thus, at the same operating frequency, the foldedslots 106 a and 106 b may have approximately the same overall length asthe linear slot 104. As shown in FIG. 1, folded slots 106 a and 106 bare Z-Slots, as each is shaped like the letter Z. In variousembodiments, other shapes may be used as well. For example, both S-Slotsand 7-Slots may be used as well (where the slot is shaped like theletter or number it is named after).

The folded slots 106 a and 106 b may also each have a rotation.Similarly as described above, a rotation of the folded slots 106 a and106 b may be adjusted with respect to the orientation of the waveguide.By rotating the folded slots 106 a and 106 b, an impedance of the foldedslots 106 a and 106 b and a polarization of the radiation may beadjusted. The radiation intensity may also be varied by such a rotation,which can be used for amplitude tapers for arraying to lower Side LobeLevel (SLL). The SLL will be discussed further with respect to the arraystructure.

FIG. 2 illustrates an example waveguide 202 with 10 radiating Z-Slots(204 a-204 j) in waveguide unit 200. As electromagnetic energypropagates down a waveguide 202, a portion of the electromagnetic energymay couple into one or more of the radiating Z-Slots (204 a-204 j) onthe waveguide 202. Thus, each of the radiating Z-Slots (204 a-204 j) onthe waveguide 202 may be configured to radiate an electromagnetic signal(in the Z direction). In some instances, each of the radiating Z-Slots(204 a-204 j) may have an associated impedance. The impedance for eachrespective radiating Z-Slot (204 a-204 j) may be a function of both thedimensions of the respective slot and the rotation of the respectiveslot. The impedance of each respective slot may determine a couplingcoefficient for each respective radiating Z-Slot. The couplingcoefficient determines a percentage of the electromagnetic energypropagating down a waveguide 202 that is radiated by the respectiveZ-Slot.

In some embodiments, the radiating Z-Slots (204 a-204 j) may beconfigured with rotations based on a taper profile. The taper profilemay specify a given coupling coefficient for each radiating Z-Slots (204a-204 j). Additionally, the taper profile may be chosen to radiate abeam with a desired beamwidth. For example, in one embodiment shown inFIG. 2, in order to obtain the taper profile, the radiating Z-Slots (204a-204 j) may each have an associated rotation. The rotation of eachradiating Z-Slot (204 a-204 j) may cause the impedance of each slot tobe different, and thus cause the coupling coefficient for each radiatingZ-Slot (204 a-204 j) to correspond to the taper profile. The taperprofile of the radiating Z-Slots 204 a-204 j of the waveguide 202, aswell as taper profiles of other radiating Z-Slots of other waveguidesmay control a beamwidth of an antenna array that includes a group ofsuch waveguides. The taper profile may also be used to control SLL ofthe radiation. When an array radiates electromagnetic energy, the energyis generally radiated into a main beam and side lobes. Typically,sidelobes are an undesirable side effect from an array. Thus, the taperprofile may be chosen to minimize or reduce the SLL (i.e. the amount ofenergy radiated in sidelobes) from the array.

FIG. 3 illustrates an example radar system 300 with six radiatingwaveguides 304 a-304 f. Each of the six radiating waveguides 304 a-304 fmay have radiating Z-Slots 306 a-306 f. Each of the six radiatingwaveguides 304 a-304 f may be similar to the waveguide 202 describedwith respect to FIG. 2. In some embodiments, a group of waveguides, eachcontaining radiating slots, may be known as an antenna array. Theconfiguration of the six radiating waveguides 304 a-304 f of the antennaarray may be based on both a desired radiation pattern and amanufacturing process for the radar system 300. Two of the components ofthe radiation pattern of the radar system 300 include a beam width aswell as a beam angle. For example, similar to as discussed with FIG. 2,a taper profile of the radiating Z-Slots 306 a-306 f of each of theradiating waveguides 304 a-304 f may control a beamwidth of the antennaarray. A beamwidth of the radar system 300 may correspond to an anglewith respect to the antenna plane (e.g. the X-Y plane) over which amajority of the radar system's radiated energy is directed.

FIG. 4 illustrates an example radar system 400 with six radiatingwaveguides 404 a-404 f and a waveguide feed system 402. The sixradiating waveguides 404 a-404 f may be similar to the six radiatingwaveguides 304 a-304 f of FIG. 3. In some embodiments, the waveguidefeed system 402 may be configured to receive an electromagnetic signalat an input port 410 and divide the electromagnetic signal between thesix radiating waveguides 404 a-404 f. Thus, the signal that eachradiating Z-Slot 406 a-406 f of each of the radiating waveguides 404a-404 f radiates may propagate in the X direction through the waveguidefeed system. In various embodiments, the waveguide feed system 402 mayhave different shapes or configurations than that shown in FIG. 4. Basedon the shape and configuration of the waveguide feed system 402 variousparameters of the radiated signal may be adjusted. For example, both adirection and a beamwidth of a radiated beam may be adjusted based onthe shape and configuration of the waveguide feed system 402.

As shown in FIG. 4, the waveguide system 400 may divide power thatenters waveguide input 410 into six radiating waveguides 404 a-404 f. Inorder to divide the power from one input into 6 outputs, the waveguidesystem may use a three level cascade system. A first level of thecascade (between plane 408 a and 408 b) may be configured to split theelectromagnetic energy from the waveguide input 410 into two first-levelbeamforming waveguides 412 a and 412 b. The waveguide system 400 mayhave a second level of the cascade (between plane 408 b and 408 c) thatmay be configured to split the electromagnetic energy from each of twofirst-level beamforming waveguides 412 a and 412 b into two respectivesecond-level beamforming waveguides 414 a-414 d for each respectivefirst-level beamforming waveguide, where one of two respectivesecond-level beamforming waveguides 414 b and 414 c for each respectivefirst-level beamforming waveguide is coupled to one of thephase-adjustment sections (shown in FIG. 6). The waveguide system 400may also have a third level of the cascade (between plane 408 c and 408d) configured to split the electromagnetic energy from one of tworespective second-level beamforming waveguides 414 a and 414 d for eachrespective first-level beamforming waveguide into two respectivethird-level beamforming waveguides 416 a-416 d for each respectivesecond-level beamforming waveguides, wherein each of the third-levelbeamforming waveguides is coupled to one of the phase-adjustmentsections (shown in FIG. 6). In some examples, the phase-adjustmentsections, which are shown in FIG. 6, may be located at plane 408 d.

FIG. 5 illustrates a network of wave-dividing channels 500 of an examplewaveguide, in accordance with an example embodiment. And FIG. 6illustrates an alternate view of the network of wave-dividing channels600, in accordance with an example embodiment.

In some embodiments, the network (e.g., beamforming network, as notedabove) of wave-dividing channels 500 may take the form of a tree ofpower dividers, as shown in FIG. 5. Each power divider (PD1-PD5) of thetop half of FIG. 5 may be constructed in a similar manner to example PD1shown in the bottom half of FIG. 5. Energy may enter the antenna throughthe input waveguide channel and is divided (i.e., split) into smallerportions of energy at each power divider, such as power divider 502, andmay be divided multiple times via subsequent power dividers so that arespective amount of energy is fed into each of the wave-radiatingchannels (energy A-F, as shown). The amount of energy that is divided ata given power divider may be controlled by a power division ratio (i.e.,how much energy goes into one channel 504 versus how much energy goesinto another channel 506 after the division). A given power divisionratio may be adjusted based on the dimensions of the corresponding powerdivider. By changing the geometry of the power divider, the ratio ofpower splitting may be controlled. For example, a length, width,separation distance, and other parameters of the power divider (shown asPD1) may be adjusted to achieve the desired power splitting ratio.

Further, each power divider and associated power division ratio may bedesigned/calculated in order to achieve a desired power taper at thewave-radiating channels. In such a case, the antenna may be designedwith a Taylor window (e.g., radiation ripples drop off at edges) orother window such that sidelobes of the antenna's far-field radiationpattern may be low. As an example, the power division ratios of thepower dividers may be set such that energy portions A, B, C, D, E, and Fare approximately 3.2%, 15.1%, 31.7%, 31.7%, 15.1%, 3.2% of the energy,respectively. Other example power divisions are possible as well.

Within examples, a technique for dividing energy between two channels504, 506 may be to use a structure of channels (i.e., a “four-portbranchline coupler”) such as that shown at the bottom of FIG. 5. In oneexample, such a technique and structure design may include a terminator508 at the end of a channel, as shown in FIG. 5 (also shown as 608 inFIG. 6), where small wedges of radio frequency-absorbing material may belocated to absorb energy that returns backwards through the channel tothat terminator 508. In another example, the waveguide structure mayfeature hybrid couplers with matched loads. The matched load may absorbsome electromagnetic energy in the waveguide.

In a further example, the waveguide structure may feature apower-dividing section that includes reactive elements that do notabsorb electromagnetic energy. Rather, the waveguides may includereactive elements may enable electromagnetic energy to be divided withminimal power losses. For example, a waveguide similar to that shown inFIG. 4 may be constructed with reactive elements. Through differentvarying of reactive components, power may be divided without having tohave a significant amount of electromagnetic energy absorbed. Therefore,because reactive components may be used in some examples rather thanenergy absorbing components, the waveguide structure may be more energyefficient.

FIG. 6 illustrates an alternate view of the network of wave-dividingchannels of FIG. 5, in accordance with an example embodiment. Thewaveguide 600 of FIG. 6 show an example representation of the variouselements described with respect to FIG. 5. For example, the waveguide600 is configured to receive a single input and output six phaseadjusted electromagnetic energy streams based on the power divisionratios of the power dividers. The six phase adjusted electromagneticenergy stream may be A, B, C, D, E, and F of FIG. 6. Additionally, FIG.6 shows six different power dividers, one of which is labeled as 602.The power dividers of FIG. 6 are organized in a manner similar toPD1-PD5 of FIG. 5. Further, FIG. 6 features a terminator 608 at the endof a channel. The terminator 608 of FIG. 6, may be similar to theterminator 508 of FIG. 5. Additionally, a terminator like terminator 608may be located at one end of each of the six waveguide channels. In somefurther examples, the terminators, like terminator 608, may have otherlocations as well. The terminators (or loads) may be located outside ofports coupled to the respective waveguides. In other examples, the portmay be located further down electromagnetic energy stream may be A, B,C, D, E, and F. Other possible location for terminators (or loads)similar to terminator 608 may be used with the present waveguide aswell.

As previously discussed, both a direction and a beamwidth of a radiatedbeam may be adjusted based on the shape and configuration of thewaveguide feed system. As discussed with respect to FIG. 5, a powertaper may determine parameters of a beam radiated by the radiatingelements coupled to the waveguide system. The angle of the transmittedbeam may be controlled by varying a phase across the six phase adjustedelectromagnetic energy streams A, B, C, D, E, and F of FIG. 6. FIG. 6also features a phase adjustment section defined by plane 604 and plane606. As shown in FIG. 6, planes 604 and 606 are shown as examples forsake of discussion.

In one example, for each of the six respective waveguides, the distancebetween planes 604 and 606 determines a phase offset for that respectivewaveguide. In one example, plane 604 may correspond to plane 408 d ofFIG. 4. Thus, if planes 604 and 606 are parallel, each waveguide mayhave the same phase offset. In some examples, when each waveguide hasthe same offset, the radiating elements coupled to the waveguide systemmay transmit a radiation beam in a broadside direction. In otherexamples, planes 604 and 606 may not be parallel. Therefore, by varyingthe angle between planes 604 and 606, and angle of the transmitted beamof the radiating elements may be adjusted.

Furthermore, phase adjustment may also be performed with lumped, orquasi-lumped, phase reversal sections. The lumped, or quasi-lumped,phase reversal sections may give a 180 degree phase reversal by using ameasured waveguide length. The lumped, or quasi-lumped, phase reversalsections may also enable phase adjustments in a coherent way to allowmore simple manufacturing of the waveguide device and also enable thewaveguide to be designed with a specific form factor.

FIG. 7 is an example method for a beamforming network for feeding shortwall slotted waveguide arrays. Although blocks 700-708 are illustratedin a sequential order, these blocks may also be performed in parallel,and/or in a different order than those described herein. Also, thevarious blocks may be combined into fewer blocks, divided intoadditional blocks, and/or removed based upon the desired implementation.

In some embodiments, some shapes and dimensions of a waveguide antennamay be highly convenient to manufacture, though other shapes,dimensions, and methods associated therewith known or not yet known maybe implemented with equal or even greater convenience. Various shapesand dimensions of portions of the manufactured waveguide antenna, suchas portions of waveguide channels formed in the antenna, includingshapes and dimensions other than those described herein, are possible aswell. Subsequent and/or intermediate blocks may be involved as well inother embodiments.

Moreover, aspects of the method of FIG. 7 may be described withreference to FIGS. 1-4 and FIG. 8, where FIG. 8 illustrates an explodedview of a portion of an example waveguide apparatus 800.

At block 700, the method includes propagating electromagnetic energy viaa waveguide in a waveguide layer. Additionally, block 700 may alsoinclude receiving electromagnetic energy by a beamforming network input.In one example, receiving electromagnetic energy by a beamformingnetwork input may be performed via a port in a bottom layer and couplingthe electromagnetic energy from the port into the waveguide.

An example waveguide layer 802 is shown in FIG. 8 along with a portionof a waveguide 804 formed into the waveguide layer. FIG. 8 shows anexample waveguide apparatus 800 in a cross-section view (i.e. the viewof FIG. 8 is as if a vertical slice of an example waveguide apparatus800 was viewed head on). Within examples, the one or more waveguidechannels formed into the waveguide layer may be routing waveguidechannels configured to direct electromagnetic waves (e.g., millimeterelectromagnetic waves), after the waves enter the waveguide antenna, tovarious radiating slots, such as the Z-Slots described above. Theseand/or other waveguide channels formed into the waveguide layer may havevarious shapes and dimensions, such as the dimensions noted above withrespect to the waveguide 102 of FIG. 1. By way of example, one or moreportions of the waveguide channels may be approximately 2.54 mm byapproximately 1.27 mm, in accordance with the internal dimensionsdescribed above, where the first metal layer 802 is approximately 2.54mm thick.

Furthermore, the bottom layer 814 may include an input port 822configured to receive electromagnetic waves into the waveguide apparatus800, which may then be propagated through the one or more waveguidechannels 804 and be radiated out the radiating element 820. Although theinput port 822 is illustrated to be directly below the radiating element820, it should be understood that, in some embodiments, that the inputport 822 may be located elsewhere in the bottom layer 814 with respectto the radiating element 820 and not located directly below theradiating element. Additionally, in some embodiments, input port 822 mayactually function as an output port to allow electromagnetic energy toleave the waveguide 804.

Referring back to FIG. 7, at block 702, the method includes splittingthe received electromagnetic energy with a cascaded set of dividers toform six electromagnetic energy streams. The splitting may be performedwith a three-level set of cascaded dividers. The first level may beconfigured to split the electromagnetic energy from the beamformingnetwork input into two first-level beamforming waveguides (such as firstlevel guides 412 a and 412 b of FIG. 4). The second level of the cascademay be configured to split the electromagnetic energy from each of twofirst-level beamforming waveguides into two respective second-levelbeamforming waveguides (guides 414 a-414 d of FIG. 4) for eachrespective first-level beamforming waveguide, wherein one of tworespective second-level beamforming waveguides (guides 414 b and 414 cof FIG. 4) for each respective first-level beamforming waveguide iscoupled to one of the phase-adjustment sections. The third level of thecascade is configured to split the electromagnetic energy from one oftwo respective second-level beamforming waveguides (guides 414 a and 414d of FIG. 4) for each respective first-level beamforming waveguide intotwo respective third-level beamforming waveguides (416 a-416 d of FIG.4) for each respective second-level beamforming waveguides, wherein eachof the third-level beamforming waveguides is coupled to a respective oneof the phase-adjustment sections.

At block 704, the method includes adjusting the phase of each of the sixelectromagnetic energy streams by six phase-adjustment sections to formsix phase-adjusted electromagnetic energy streams. As shown in FIG. 6,the phase of each electromagnetic energy stream may be adjusted based ona length of the phase-adjustment section of the respective waveguide. Bylengthening a waveguide, an electromagnetic wave will propagate furtherin the waveguide, providing a phase offset. Conversely, by shortening awaveguide, an electromagnetic wave will propagate a shorter distance inthe waveguide, providing a phase offset. Therefore, each waveguide mayhave an associated lengthening or shortening in the phase-adjustmentsection in order to provide a phase offset. The phase offset across theset of waveguides may adjust a transmission angle of a beam transmittedby antennas associated with the waveguides.

At block 706, the method includes coupling each of the six phaseadjusted electromagnetic energy streams into a respective radiatingwaveguide of six radiating waveguides located in a waveguide layer,where each radiating waveguide is coupled to at least one radiatingelement located in a radiating layer. As shown in FIG. 4, each of theradiating waveguides 404 a-404 f may include at least one radiatingelement 406 a-406 f. The output from the phase-adjustment section of thewaveguides (A-F of FIG. 6) may be coupled into the radiating waveguides404 a-404 f. Thus, each radiating waveguide may receive electromagneticenergy that has been both (i) adjusted for phase and (ii) had an appliedpower taper factor.

At block 708, the method includes for each radiating waveguide,radiating at least a portion of the phase adjusted electromagneticenergy stream by a radiating element. By way of example, as shown inFIG. 8, the top layer 812 may include at least one radiating structure820. The radiating structure 820 may be etched, cut, or otherwiselocated on sheet of metal that is adhered to the middle layer 802. Theradiating structure 820 may be configured to radiate electromagneticenergy coupled from inside the waveguide 804 out into free space (i.e.the radiating structure converts the guided energy in the waveguide 804into unguided energy propagating in free space).

In some embodiments, at least a portion of the one or more waveguidechannels may be formed into at least one of the radiating and bottommetal layers. For instance, a first portion of the one or more waveguidechannels may be formed into the radiating metal layer, whereas a secondportion and third portion of the one or more waveguide channels may beformed into the waveguide and bottom metal layers, respectively, wherethe second and third portions may or may not be identical. In suchembodiments, when the radiating, waveguide, and bottom layers arecoupled together, the layers may be coupled together such that theportions of the one or more waveguide channels of the second and/orthird layers are substantially aligned with the first portion of the oneor more waveguide channels of the first metal layer, thus forming one ormore waveguide channels in the waveguide antenna that may be configuredto propagate electromagnetic waves (e.g., millimeter electromagneticwaves). In this example, a width of the waveguide may be wider than thewidth of the waveguide layer, as a portion of the waveguide may also belocated in the radiating layer and/or the bottom layer.

In other embodiments, the one or more waveguide channels may be formedentirely in the waveguide metal layer. In such other embodiments, theradiating and bottom metal layers may include other elements that may beconfigured to facilitate radiation of electromagnetic waves. Forinstance, as shown in FIG. 8, the radiating metal layer may include aradiating element 820, such as a radiating element that comprises a slotconfigured to radiate electromagnetic waves out of the waveguideapparatus 800, such as millimeter electromagnetic waves. The slot mayhave a rotational orientation relative to a dimension of the one or morewaveguide channels. For example, the slot may be a Z-Slot or anothertype of slot.

It should be understood that various processes, including but notlimited to those described above, may be involved with the radiating,waveguide, bottom, and/or additional layers. It should also beunderstood that arrangements described herein are for purposes ofexample only. As such, those skilled in the art will appreciate thatother arrangements and other elements (e.g. machines, apparatuses,interfaces, operations, orders, and groupings of operations, etc.) canbe used instead, and some elements may be omitted altogether accordingto the desired results. Further, many of the elements that are describedare functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in anysuitable combination and location.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the scope beingindicated by the following claims.

What is claimed is:
 1. A radar system comprising: six radiatingwaveguides located in a waveguide layer, each having a radiatingwaveguide input, wherein each radiating waveguide has a height and awidth that are equal to that of each other radiating waveguide, whereinthe radiating waveguides are aligned on a plane defined by a center ofthe width of the radiating waveguide and a length of the radiatingwaveguide, and wherein each radiating waveguide is coupled to at leastone radiating element located in a radiating layer; and a beamformingnetwork located in the waveguide layer, wherein the beamforming networkcomprises: a beamforming network input, six beamforming network outputs,wherein each beamforming network output is coupled to one of theradiating waveguide inputs, six phase-adjustment sections, wherein eachof the phase-adjustment sections is coupled to a respective one of sixcascade outputs, a cascaded set of dividers configured to splitelectromagnetic energy from the beamforming network input to the sixphase-adjustment sections, wherein the cascade comprises: a first levelof the cascade configured to split the electromagnetic energy from thebeamforming network input into two first-level beamforming waveguides, asecond level of the cascade configured to split the electromagneticenergy from each of two first-level beamforming waveguides into tworespective second-level beamforming waveguides for each respectivefirst-level beamforming waveguide, wherein one of two respectivesecond-level beamforming waveguides for each respective first-levelbeamforming waveguide is coupled to one of the phase-adjustmentsections, and a third level of the cascade configured to split theelectromagnetic energy from one of two respective second-levelbeamforming waveguides for each respective first-level beamformingwaveguide into two respective third-level beamforming waveguides foreach respective second-level beamforming waveguides, wherein each of thethird-level beamforming waveguides is coupled to a respective one of thephase-adjustment sections.
 2. The radar system according to claim 1,wherein the first level of the cascade is configured to divide powerevenly between the two first-level beamforming waveguides.
 3. The radarsystem according to claim 1, wherein each radiating waveguide of the sixwaveguides has a predetermined amplitude taper factor, and wherein thebeamforming network is configured to provide an electromagnetic signalhaving an amplitude proportional to the associated amplitude taperfactor of the respective radiating waveguide to the radiating waveguideinput of the respective radiating waveguide.
 4. The radar systemaccording to claim 1, wherein the cascaded set of dividers comprisesreactive elements.
 5. The radar system according to claim 1, wherein thecascaded set of dividers comprises hybrids each having matched loads. 6.The radar system according to claim 1, wherein the beamformingwaveguides each have a width equal to the width of the radiatingwaveguides.
 7. The radar system according to claim 1, wherein eachradiating waveguide of the six waveguides has a predetermined phaseshift defined by a length of a corresponding phase-adjustment section.8. The radar system according to claim 1, wherein each radiatingelement: comprises a respective slot defined by a respective angular orcurved path, and has an effective length greater than the height ofwaveguide, wherein the effective length is measured along the respectiveangular or curved path of the respective slot.
 9. The radar systemaccording to claim 1, wherein the radiating element is configured tooperate at approximately 77 Gigahertz (GHz) and propagate millimeter(mm) electromagnetic waves.
 10. A method of radiating electromagneticenergy comprising: receiving electromagnetic energy by a beamformingnetwork input; splitting the received electromagnetic energy with acascaded set of dividers to form six electromagnetic energy streamscoupled into six phase-adjustment sections, wherein the splittingcomprises: splitting the electromagnetic energy from the beamformingnetwork input into two first-level beamforming waveguides by a firstlevel of the cascade, splitting the electromagnetic energy from each oftwo first-level beamforming waveguides into two respective second-levelbeamforming waveguides for each respective first-level beamformingwaveguide by a second level of the cascade, wherein one of tworespective second-level beamforming waveguides for each respectivefirst-level beamforming waveguide is coupled to one of thephase-adjustment sections, and splitting the electromagnetic energy fromone of two respective second-level beamforming waveguides for eachrespective first-level beamforming waveguide into two respectivethird-level beamforming waveguides for each respective second-levelbeamforming waveguides by a third level of the cascade, wherein each ofthe third-level beamforming waveguides is coupled to a respective one ofthe phase-adjustment sections; adjusting the phase of each of the sixelectromagnetic energy streams by the six phase-adjustment sections toform six phase adjusted electromagnetic energy streams; coupling each ofthe six phase adjusted electromagnetic energy streams into a respectiveradiating waveguide of six radiating waveguides located in a waveguidelayer, wherein each radiating waveguide is coupled to at least oneradiating element located in a radiating layer; and for each radiatingwaveguide, radiating at least a portion of the phase adjustedelectromagnetic energy stream by a radiating element.
 11. The methodaccording to claim 10, further comprising dividing power evenly betweenthe two first-level beamforming waveguides by the first level of thecascade.
 12. The method according to claim 10, wherein each radiatingwaveguide of the six waveguides has an predetermined amplitude taperfactor, and further comprising providing an electromagnetic signalhaving an amplitude proportional to the associated amplitude taperfactor of the respective radiating waveguide to a radiating waveguideinput of the respective radiating waveguide.
 13. The method according toclaim 10, wherein the cascaded set of dividers comprises reactiveelements.
 14. The method according to claim 10, wherein the cascaded setof dividers comprises hybrids each having matched loads.
 15. The methodaccording to claim 10, wherein the beamforming waveguides each have awidth equal to the width of the radiating waveguides.
 16. The methodaccording to claim 10, wherein each radiating waveguide of the sixwaveguides has an predetermined phase shift defined by a length of acorresponding phase-adjustment section.
 17. The method according toclaim 10, wherein each radiating element: comprises a respective slotdefined by a respective angular or curved path, and has an effectivelength greater than the height of waveguide, wherein the effectivelength is measured along the respective angular or curved path of therespective slot.
 18. The method according to claim 10, wherein theelectromagnetic energy has a frequency of approximately 77 Gigahertz(GHz).
 19. A beamforming network located in a waveguide layercomprising: a beamforming network input, six beamforming networkoutputs, wherein each beamforming network output is coupled to arespective waveguide input of a set of waveguides, a cascaded set ofdividers coupled to six phase-adjustment sections, where the cascade isconfigured to distribute electromagnetic energy from the beamformingnetwork input to the six phase-adjustment sections based on apredetermined taper profile, wherein the cascade comprises: a firstlevel of the cascade configured to approximately evenly split theelectromagnetic energy from the beamforming network input into twofirst-level beamforming waveguides, a second level of the cascadeconfigured to split the electromagnetic energy from each of twofirst-level beamforming waveguides into two respective second-levelbeamforming waveguides for each respective first-level beamformingwaveguide, wherein one of two respective second-level beamformingwaveguides for each respective first-level beamforming waveguide iscoupled to one of the phase-adjustment sections, and a third level ofthe cascade configured to split the electromagnetic energy from one oftwo respective second-level beamforming waveguides for each respectivefirst-level beamforming waveguide into two respective third-levelbeamforming waveguides for each respective second-level beamformingwaveguides, wherein each of the third-level beamforming waveguides iscoupled to a respective one of the phase-adjustment sections; andwherein each phase-adjustment section has a respective length thatprovides a respective phase offset for each waveguide.
 20. Thebeamforming network according to claim 19, wherein the beamformingnetwork is configured to operate at approximately 77 Gigahertz (GHz).